A silicon carbide (SiC) substrate has a very small thermal diffusion coefficient of impurities and cannot practically use a thermal diffusion process of impurities. For this reason, in order to control electrical conductivity of the SiC substrate, there is a need to activate impurities by performing ion implantation of the impurities into the SiC substrate and annealing treatment of the SiC substrate at about 1500° C. to about 2000° C.
Prior to performing the activation annealing treatment, the inside of a furnace is preheated so as to increase the inside of the furnace to a predetermined temperature. For example, Patent Literature 1 discloses a technology of preheating the inside of a furnace followed by carrying a treated substrate in a heating furnace and carrying the treated substrate in the furnace after the inside of the furnace reaches a predetermined temperature, in a method for performing annealing treatment on the treated substrate with a halogen lamp.
Further, Patent Literature 2 discloses a technology of ending preheating when a heating-up time is within a predetermined value, in performing the preheating by repeating a series of processes which a dummy substrate is carried in and out of a lamp anneal apparatus by the real processes.